1. Field of the Invention
The invention relates generally to chip forming cutting tools. More particularly the invention concerns face milling cutters having adjustment mechanisms for finely controlling the axial extent of a cutting bit or insert beyond the cutting face of the mill, i.e. face runout.
2. Description of the Prior Art
Cutting tools with adjustable cutting element positions are known wherein the cutting elements or inserts are adjusted by providing a flexible portion of the toolholder body or of an insert holding cartridge. Also in this class of adjustable cutting tools are those using camming elements to deform an insert holding blade elastically so as to alter the projection of the cutting tip beyond a predetermined reference plane. Examples of this known class of cutting tools are set forth in the following U.S. Pat. Nos. 3,282,133--Dickinson et al.; 3,675,290--Mayer, July 11, 1972; 3,802,043--Garih, Apr. 9, 1974; 3,834,829--Munro, Sept. 10, 1974; 4,040,156--Tack, Aug. 9, 1977.
Use of polycrystalline diamond tipped cutting inserts has created milling applications utilizing relative high surface speeds. To generate acceptably smooth surfaces at these higher speeds, each cutting portion or tip of each insert must be very precisely positioned relative to the other inserts of the milling cutter.
The Mayer and Tack patents dislcose adjusting concepts which limit the usable shape of the cutting inserts or the lead angle at which they can be mounted, since the adjustment is effected by a flexible tongue riding along a sloping surface of the insert to impart linear sliding motion of the insert along a wall of its associated mounting pocket. Such friction generating insert motion has the further disadvantage of not offering smoothly attainable, ultra fine adjustment accuracy required in higher speed milling applications.
The Mayer, Garih and Tack patents disclose concepts suffering from the further disadvantage that bi-directional adjustment of the cutting tip is not attainable with the adjustment actuating means disclosed. Even unidirectional adjustment utilizing the teachings of Mayer and Tack is not possible without first loosening the insert retention apparatus. Similarly, the Munro boring tool inserts cannot be bi-directionally adjusted without first loosening a cone point screw engaging the insert to be moved.
Dickinson et al. teaches adjustable boring tools requiring sawcuts or slots formed in the tool holder body itself and is therefore not applicable to a multi-insert cutting tool where each insert must be independently adjustable. This approach also limits the size and bulk of the tool body and, since the adjusting actuator directly engages one or both walls of the slot, limits the physical location of the actuating element and slot with respect to the insert to be adjusted.
A need has therefore been shown, especially in high speed milling applications, for a cutting tool with very finely adjustable cutting inserts in which the cutting portion of each insert can be minutely altered in two directions with respect to a reference surface of the cutting tool body.